One woman is dead and two others were injured in a highway crash just south of Three Hills, Alta., on Saturday, about 120 kilometres northeast of Calgary.

RCMP say just after noon, a Jeep travelling southbound on Highway 21 hit the back of truck pulling a trailer as it waited for a vehicle to turn left into the Braconnier Reservoir campground.

Upon impact, the Jeep flipped into the northbound lane of the highway and collided with a motorcycle.

The 34-year-old woman riding the motorcycle was airlifted to Calgary hospital with critical head injuries, but died en route.

Another man and woman were taken by ambulance to the Three Hills Health Centre in stable condition. Their injuries are not life-threatening.

Investigators are trying to determine the cause of the accident, but RCMP say alcohol is not believed to be a factor but do suspect excessive speed may have played a role.